Photographic colloid transfer system



United States Patent Ofifice 3,326,687 Patented June 20, 1967 This invention relates to colloid transfer photographic materials, more particularly to light sensitive materials which are suitable for roomlight handling.

In the photographic colloid transfer system, as described in Yutzy et al. US. Patents 2,596,756 and 2,716,- 059, an unhardened silver halide photographic emulsion containing a tanning developer is exposed to an image and after sufiicient development, the developing silver halide emulsion is pressed against a surface to transfer a stratum of unexposed, untanned gelatin to the receiving surface. In this way, a positive image is obtained of the exposed image.

In one embodiment of colloid transfer, the silver halide emulsion used for office copying purposes is handled in roomlight so that there is a need for adding a substance to the emulsion which acts to reduce the emulsion speed to a level which will permit roomlight handling in light, such as fluorescent light, rich in blue light. However, it is necessary to preserve the sensitivity of the emulsion t incandescent lamps, sufficiently to permit exposure on the office copying apparatus.

Methylene blue has been proposed for this purpose. However, methylene blue has not been entirely satisfactory since it interferes with certain spectral sensitizess causing a loss in sensitized speed which is reflected in rerequiring increased exposure. In some instances, the incorporated developer causes the emulsion containig methylene blue to'become resensitized both to the printing light and to roomlight. Moreover, there is a limited desensitization possible with methylene blue, since the desensitization approaches a maximum asymptotically as the concentration is increased.

It has been desirable to find an additive for the unhardened colloid transfer type emulsions which contain tanning type silver halide developers, whichwould overcome the disadvantages of methylene blue. However, such an additive needs to be stable to provide for good keeping. It needs to be inert to the incorporated developers in the emulsion and to be compatible with both methylene blue and the silver halide emulsions. In addition, the additive should not interfere with the tanning action of the developer on the colloid such as gelatin in the exposed non-image areas so that poor transfers result.

I have found that certain quaternarized derivatives of 1,2-bis (4-pyridyl)ethylene can be used to overcome some of the deficiencies of methylene blue in the colloid transfer emulsions.

One object of this invention is to provide an unhardened silver halide emulsion containing a desensitizer which permits roomlight handling of the emulsion without seriously reducing its sensitivity to the printing light. A further object is to provide a l,2-bis(4-pyridyl)ethylene desensitized colloid transfer silver halide emulsion which has improved desensitization with respect to that obtained from methylene blue and reduced interference with the tanning action of the tanning developer.

The above objects are attained by incorporating into an unhardened silver halide emulsion at least one quaternarized derivative of 1,2-bis (4-pyridyl)ethylene. derivative may have the following structure:

CH=CH The e To

where A useful method of incorporatnig a derivative which is not water soluble is to dissolve it in a small amount of a water-miscible solvent such as, for example, acetone, methanol, ethanol, etc.

In our preferred embodiment 0.5 to 3 grams of the quaternarized derivative of 1,2-bis(4-pyridyl)ethylene per mole of silver halide are added to a spectrally sensitized, substantially unhardened colloid silver halide emulsion containing a tanning silver halide developer.

Although our preferred emulsion is a silver chloride emulsion, other silver halide emulsions can be used, including silver bromide, silver iodide, silver chlorobromide, silver chloroiodide, silver bromoiodide and silver chlorobromoiodide. Mixtures of these may also be used.

The tanning developers which may be used are those disclosed in the above US. patents describing colloid transfer emulsions. In addition, non-tanning ilver halide developers may be incorporated in the emulsions as described in the above patents or used in the developing solution to improve the density of the transferred image.

The colloid transfer emulsions of this invention may also be used to prepare lithographic plates, and the emulsions of this invention may be exposed either by the reflex method or through appropriate optical systems. de-

, pending upon the speed of the emulsionused, the desired result, etc.

The concentration of the tanning developing agent in the emulsion is dependent in part upon the result desired but can be of the order of 350 grams of tanning developing agent per kilogram ofsilver nitrate converted to silver halide, used in making the emulsion, to obtain good density of about 250 grams per kilogram of silver nitrate to obtain adequate density and an emulsion having optimum keeping properties. a

The photographic emulsion layer used in this process can be a dispersion of silverihalide grains in a colloid vehicle such as gelatin or, in a resin such as polyvinyl alcohol, polyacrylamide, etc., capable of being differentially tanned.

It is necessary for the successful operation of the invention that the emulsion layer be not harder than would be the case with gelatin containing 0.25 ounce of formaldehyde solution (40 percent diluted 1:3 with water); or 0.7 gram of dry formaldehyde per pound when freshly coated; or 0.1 ounce of the solution per pound for a sample aged 3 to 6 months. By substantially unhardened as used herein, and in the appended claims, it is to be understood that this means a hardness of the order obtained with gelaamass? tin treated with formaldehyde under the conditions above.

The following examples are intended to illustrate my invention but not to limit it in any way.

A substantially unhardened gelatino-silver halide emulsion containing 1 mole of silver chloride, 300 grams of gelatin and 5700 grams of water is gelled, noodled and washed for one-half hour with water, then melted at 40 C., and the following addition made:

650 grams of 8 percent aqueous saponin 600 grams of a dispersion of 4-phenylcatechol prepared by dissolving 50 grams of 4-phenylcatechol in 70 grams of dibutyl phthalate at 80 C. and pouring it into a vigorously stirred solution of 50 grams of gelatin in 50 grams of 8 percent aqueous saponin solution and 500 ccs. of water at 40 C.

To samples of this emulsion is added a green sensitizing merocyanine dye and to each sample to be tested, a desensitizer in an amount as shown in the table below. The emulsion is coated at 190 mg. of silver per square foot on a paper support and dried.

The results shown in the table below were obtained by testing with light, which simulated blue light, and also with white light in which the light to which the emulsion is inherently sensitive had been removed. The test using the Wratten No. 4 filter indicate the response of the emulsion to white light which has the light to which the emulsion is inherently sensitive, removed therefrom. The test using the Wratten No. 35 and 38A filters shows the response to white light in which all wavelengths of the spectrum have been removed except for the blue light. Each set of samples are grouped under a control containing methylene blue, indicating the data obtained at the same time as the given control. In order to obtain sensitometric data, the exposed test strips were processed using D-72 developer for one minute.

To obtain transfer performance data, the coatings in each instance were exposed on a Verifax Regent Copier to incandescent light for 20 seconds, immersed for 60 seconds in an activator solution having the following composition:

Grams Na CO -H O Urea 50 Water to 1 liter.

held at a temperature of 81 F. and rolled in contact with Verifax receiving paper.

l Desensitizer A has the following structure:

E 01- 5 ll Desensitizer B is an oxoniurn salt of the following structure:

/@C CHCH=CH- N oHa)z-(B1M)- ea 0.119

The emulsion of this invention can be coated on various supports such as paper, glass, and the like. In a useful embodiment, the unhardened emulsion can be coated on a porous base material and after developing in an alkaline activator it can be washed with hot water to provide a stencil master. The particular fabric useful for this embodiment depends, of course, on the ultimate result desired. However, tea bag stock may be used as well as silk screen stock, and the like, customarily used for the silk screens process. If desired, the emulsion can be exposed, developed and contacted against a receiving support to remove the unhardened areas of the emulsion. After this step, a subsequent Washing step may be used, if needed, to remove the additional unhardened emulsion which remains in the interstices of the fabric.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A substantially unhardened hydrophilic colloid silver halide emulsion containing a colloid tanning silver halide Blue Speed (Wratten Spectral Sensitization Nos. 35-1-38 Filters) (Wratten No. 4 Filter) Room-light Teler- Printing Speed Coating No. Desensitizer (gJAg. mole) M100 Control) (R61. to Control) Rel. Speed Fog Rel. Speed Fog Methylene Blue (0.03) 100.0 0.43 23 .0 0 Control. A 17 .2 0.20 3 .2 0.19 Very much lower. Methylene Blue (0.03)... 100 .0 0.20 145 .0 0.25 Control Control.

.0)* 120 .0 0 .14 209 .0 0.17 Lower Slightly higher. Methylene Blue (0 03). 100.0 0.10 126 .0 0.12 Control Control. Compound I (0 O3) 162.0 0.10 589 .0 0.10 Equal 4 times higher. Methylene Blue (0 03) 100 .0 0 .05 105 .0 0 .04 Control Control. Compound 11 (0.04).-. 148 .0 0.03 229 .0 0.02 Much Higher. Equal. Compound III (0.05) 289 .0 0.03 741.0 0 .04 Lower 20 times higher.

This desensitizer interferes with the tanning action of the developer on the gelatin in the exposed, nonimage areas and thus results in poor transfers.

Desensitizers (I) 1,2-bis(l-phenacyl-4-pyridiniurn bromide)ethylene 6 (II) l,2-bis(1-methyl-4-pyridiniurn p-toluenesulfonate) ethylene (III) 1,2-bis(4-pyridyl-1-sulfopropyl)ethylene Methylene Blue, also called 3,7-bis(dimethyamino)- phenazathioniurn chloride, is a sulfonium salt of the following structure:

developing agent and a desensitizing amount of a de sensitizing compound which is a quaternarized derivative of a 1,2-bis(4-pyridyl)ethylene.

2. An emulsion of claim 1 in which the l,2-bis(4-pyridyl)ethylene has the general formula:

-C1=CH e f T e; x R R X where R represents a group selected from the class consisting of phenacyl, alkyl and substituted alkyl in which the alkyl moiety has from 110 carbon atoms, X represents an anion except where R is a sulfoalkyl derivative and the negative charge is assumed by the sulfoalkyl group itself. 3. An emulsion of claim 1 in which the colloid is gelatin. 7

4. An emulsion of claim 1 in which the colloid is gelatin and the 1,2-bis (4-pyridyl)ethylene has the general formula:

CH=CH CH=CH \N X it where R represents a group selected from the class consisting of phenacyl, alkyl and substituted alkyl in which the alkyl moiety has from 1-10 carbon atoms,

X represent an anion except when -R is a sulfoalkyl derivative and the negative charge siassumed by the sulfonalkyl group itself,

and in which the proportion of desensitizing compound is from 0.5 to 3 grams per mole of silver halide.

7. An emulsion of claim 1 in which the colloid is gelatin and the proportion of desensitizing compound is from 0.5 to 3 grams per mole of silver halide.

8. An emulsion of claim 1 in which the desensitizing compound is 1,2-bis(1-phenacyl-4-pyridinium bromide) ethylene.

9. An emulsion of claim 1 in which the desensitizing compound is 1,2-bis(1-metl1yl-4-pyridinium p-toluenesulfonate)ethylene.

10. An emulsion of claim 1 in which the desensitizing compound is 1,2-bis (4-pyridyl-1-sulfopropyl)ethylene.

11. A process of preparing a substantially unhardened colloid silver halide emulsion for roomlight handling comprising dissolving in a water-miscible solvent a desensitizing compound which is a quaternarized derivative of a 1,2-bis(4-pyridyl)ethylene and adding a desensitizing amount to the substantially unhardened colloid silver halide emulsion.

12. A process of claim 11 in which the colloid is gelatin.

13. A process of claim 11 in which the desensitizing compound has the general formula:

Gonzo].

r \N R where R represents a group selected from the class consisting of phenacyl, alkyl and substituted alkyl in which the alkyl moiety has from 1-10 carbon atoms,

X represents an anion except when R is a sulfoalkyl derivative and the negatve charge is assumed by the sulfoalkyl group itself.

14. A process of claim 11 in which the colloid is gelatin and the desensitizing compound has the general formula:

fe X it R X where R represents a group selected from the class consisting of phenacyl, alkyl and substituted alkyl in which the alkyl moiety has from -l-10 carbon atoms,

X represents an anion except when R is a sulfoalkyl derivative and the negative charge is assumed by the sulfoalkyl group itself,

and the desensitizing compound is added in an amount of 0.5 to 3 grams per mole of silver halide.

References Cited UNITED STATES PATENTS 2,596,756 5/1952 Yutzy et a1. 9628 3,035,917 5/1962 Fry 96101 3,124,458 3/1964 Fry 96-101 NORMAN G. TORCHIN, Primary Examiner.

V. P. CANNEY, Assistant Examiner. 

1. A SUBSTANTIALLY UNHARDENED HYDROPHILIC COLLOID SILVER HALIDE EMULSION CONTAINING A COLLOID TANNING SILVER HALIDE DEVELOPING AGENT AND A DESENSITIZING AMOUNT OF A DESENSITIZING COMPOUND WHICH IS A QUATERNARIZED DERIVATIVE OF A 1,2-BIS(4-PYRIDYL)ETHYLENE.
 2. AN EMULSION OF CLAIM 1 IN WHICH THE 1,2-BIS(4-PYRIDYL)ETHYLENE HAS THE GENERAL FORMULA: 